Perth Bugle has turned into a rumour monger (4,9)
I believe the answer is:
bush telegraph
'a rumour monger' is the definition.
The definition suggests a singular noun which matches the answer.
'perth bugle has turned' is the wordplay.
'turned' indicates anagramming the letters.
'perth'+'bugle'+'has'='perthbuglehas'
'perthbuglehas' with letters rearranged gives 'BUSH TELEGRAPH'.
'into' acts as a link.
Can you help me to learn more?
(Other definitions for bush telegraph that I've seen before include "Supposed means of passing the word around" , "Informal communications network" , "Gossip network" , "Message-bearer" , "Rapid transmission of information (including a newspaper)" .)